prog8/examples/cx16/keyboardhandler.p8

79 lines
2.8 KiB
Plaintext
Raw Normal View History

%import textio
%zeropage basicsafe
%option no_sysinit
; The documentation for custom PS2 key handlers can be found here:
2023-03-12 15:09:55 +00:00
; https://github.com/X16Community/x16-docs/blob/master/X16%20Reference%20-%2002%20-%20Editor.md#custom-keyboard-scancode-handler
main {
sub start() {
txt.print("custom key handler test - press keys! esc to quit!\n")
sys.set_irqd()
uword old_keyhdl = cx16.KEYHDL
cx16.KEYHDL = &keyboard_scancode_handler
sys.clear_irqd()
while handle_keyboard_event() {
}
sys.set_irqd()
cx16.KEYHDL = old_keyhdl
sys.clear_irqd()
}
; Keyboard handler communication variables.
; these need to be in block scope instead of in a subroutine,
; so that they won't get overwritten with initialization values every time.
; The assembly keyboard handler will set these, prog8 will read them.
bool @shared keyhdl_event ; is there a keyboard event to handle?
ubyte @shared keyhdl_scancode
sub handle_keyboard_event() -> bool {
; Potentially handle keyboard event.
; Note that we do this from the program's main loop instead of
; the actual keyboard handler routine itself.
; The reason for this is documented below in the handler assembly routine.
if not keyhdl_event
return true
keyhdl_event = false
txt.print_ubhex(keyhdl_scancode, true)
txt.spc()
if keyhdl_scancode & $80
txt.chrout('u')
else
txt.chrout('d')
txt.nl()
return keyhdl_scancode!=$6e ; escape breaks the loop
}
asmsub keyboard_scancode_handler() {
; NOTE that the keyboard handler is an asm subroutine.
; Unfortunately is it not possible to use prog8 code or calls here,
; because the X register gets overwritten here by the kernal.
; Pog8 uses the X register internally (for the software eval stack).
; So it is unsafe to call prog8 code from here because the evaluation stack pointer
; will be invalid which produces undefined results.
; So, instead, we store the various keyboard event bytes and signal
; the main prog8 program that a keyboard event has occurred.
; It then processes it independently from the assembly code here.
;
; Unfortunately this also means you cannot decide easily from that prog8 code
; if the keyboard press should be consumed/ignored or put into the keyboard queue
; (this is controlled by returning 0 or 1 in register A here)
%asm {{
pha
sta keyhdl_scancode
lda #1
sta keyhdl_event
pla
lda #0 ; By setting A=0 we will eat this key event. leave A unchanged to pass it through.
rts
}}
}
}